[Bugfix] Bugfix for getting maximum matching length of conditional ma…

…rk. (sonic-net#14515)

Description of PR
We changed the matching rule of conditional mark in PR sonic-net#14395. There is a bug when getting the maximum matching length. In this PR, we fix this bug.

Approach
What is the motivation for this PR?
We changed the matching rule of conditional mark in PR sonic-net#14395. There is a bug when getting the maximum matching length. In this PR, we fix this bug.

co-authorized by: jianquanye@microsoft.com

tests/common/plugins/conditional_mark/__init__.py

@@ -428,7 +428,7 @@ def find_all_matches(nodeid, conditions):
         marks = match[case_starting_substring].keys()
         for mark in marks:
             if mark in conditional_marks:
-                if length > max_length:
+                if length >= max_length:
                     conditional_marks.update({
                         mark: {
                             case_starting_substring: {
@@ -441,6 +441,7 @@ def find_all_matches(nodeid, conditions):
                         case_starting_substring: {
                             mark: match[case_starting_substring][mark]}
                     }})
+                max_length = length
 
     # We may have the same matches of different marks
     # Need to remove duplicate here